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题库 / Prep2007E1-DS-142
If x is a positive integer, what is the least common multiple of x, 6, and 9 ?
(1) The least common multiple of x and 6 is 30.
(2) The least common multiple of x and 9 is 45.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
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(1) X和6(2*3) 并集为 5*2*3: 可知 x一定有5，可能有2和3，而且就算有的话，最大的个数也就是一个2，一个3，和一个5. 所以不管是什么情况，x和6（2*3）,9 （3*3)并集都一定是 5*2*3。(2)同(1)一样的思想，通过并集去判断。
如果是最小公倍数的话就是交集。
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